Title:
The Behaviour of Ash Forming Elements in Waste Wood Operated Large-Scale Updraft Gasifiers with Subsequent Gas Combustion
Author(s):
Supancic, K., Benesch, C., Crane, M., Brothwell, P., Obernberger, I.
Document(s):
Paper
Abstract:
A detailed analysis of the fate of aerosol and deposit forming elements in an industrial scale waste-wood-fired updraft gasifier (fuel heat input 36 MW) is presented. The work included a comprehensive analysis of all mass flows (fuel, bottom ash, fly ash, additives and flue gas) followed by mass and element balances for selected evaluation periods to determine the release rates of the relevant aerosol and deposit forming elements from the fuel bed to the gas phase. The results show that especially Cl, Zn and Pb are very unevenly distributed over the fuel and their real concentration in the fuel is obviously significantly higher than the analyses results of the fuels indicate. The results of high temperature thermodynamic equilibrium calculations showed that elevated Cl contents are the reason for the observed high release rates of K and Na (compared to updraft gasifiers operated with virgin wood). Finally, the impact of the ash forming elements released from the fuel bed with the gas on boiler deposits was investigated by 1D simulations of aerosol and ash deposit formation by a specially developed software. The results showed that elevated contents of Cl, Zn, Pb, K, Na and S lead to increased boiler deposits which was also confirmed by measurements. Zn and Pb compounds amount to almost 50 wt% of the boiler deposits. The main share of the deposits are originally formed as chlorides and ZnO, but get quickly sulphated once they are deposited on the boiler tubes.
Keywords:
aerosols, gasification, mass balance, waste, industrial scale application, combined heat and power generation (CHP)
Topic:
Biomass Conversion for Bioenergy
Subtopic:
Biomass Combustion in Large Utilities
Event:
29th European Biomass Conference and Exhibition
Session:
2AO.8.4
Pages:
425 - 434
ISBN:
978-88-89407-21-9
Paper DOI:
10.5071/29thEUBCE2021-2AO.8.4
Price:
FREE
